New York, American Telephone and Telegraph Company, 1933. Royal8vo. Original full blue cloth. Volume XI!, 1933 of ""The Bell System Technical Journal"". Library stamp to front free end-paper. Minor bumping to extremities. A nice and clean copy. Pp. 377-430. [Entire volume: 7, (1), 537 pp.].
First edition of Fletcher and Munson's important paper in which they proved that loudness not only varies in intensity but also in frequency. Fletcher is today widely regarded as the father of stereophonic sound.